Dissipative force modulation Kelvin probe force microscopy applying doubled frequency ac bias voltage

The authors propose a surface potential measurement technique using dissipative force modulation (DM) method with an ac bias voltage of doubled harmonic frequency ( 2 ω ) of the oscillating cantilever ( 2 ω DM method). The effect of the stray capacitance between a cantilever and a sample on electrostatic force spectroscopy/Kelvin probe force microscopy measurement is almost completely removed in 2 ω DM method, since the distance dependence of the modulated electrostatic force increases from 1 ∕ z to 1 ∕ z 2 . 2 ω DM method has an advantage of high force sensitivity due to the high Q factor of the cantilever in vacuum. The authors demonstrate quantitative surface potential measurement by using dissipative tip-sample interactions.